This invention relates generally to displaying image information and more particularly, to overlaying graphical objects on medical image object.
In at least one known imaging system shapes, or data, are overlaid on images generated by the imaging system. The shapes define certain areas of interest, such as regions of interest, volumes of interest, shapes used to measure a distance, tick marks, and grids. However, the simultaneous displaying of the medical image and the shapes cause difficulty for an operator of the imaging system attempting to utilize the displayed image and shapes.
More specifically, the solid lines of the shape hides, or covers, a portion of the anatomy displayed in the medical image. This hiding of the anatomy causes significant errors in small measurements and detracts from the quality of the diagnosis. In addition, the solid borders of these shapes may also lead to diagnostic errors when determining statistics. Additionally, when determining an area of the image within a closed shape, it is difficult for the operator to determine whether pixels covered by the shape are counted as part of the area, or whether the shape defines the outside of the area and only the pixels inside contribute towards the area.
It is desirable to provide a system which displays shapes without totally obscuring the medical image. It would also be desirable to provide such a system which fills or outlines the shapes for defining the area covered by the shape.
These and other objects may be attained in a system which, in one embodiment, includes a overlay algorithm that generates graphical objects for display on image objects. More particularly and in one embodiment of the present invention, a medical imaging system generates medical image objects. Graphical objects are then generated, based upon an input from a operator or user, and displayed with the image objects. The graphical objects may be used to measure a distance or select a portion of the medical image. In one embodiment, each graphical object has an opacity value less than the image objects so that when the graphical objects are combined with the image objects, the graphical objects do not obscure any information contained in the image object. More specifically, after sorting the objects in a back to front procedure, a destination value, Cd, for each component is determined in accordance with:       C    d    =      min    ⁡          (                        k          A                ,                              Cs            *                          (                                                A                  s                                                  k                  A                                            )                                +                                    C                              d                -                1                                      ⁡                          (                              1                -                                                      A                    s                                                        k                    A                                                              )                                          )      
where:
As equals an alpha value for a source; and
kA=2mcxe2x88x921, where Mc equals a number of bitplanes in an alpha component and kA is between zero and one.
Cdxe2x88x921 is a previous destination value of a single component of the image object;
Cs is a source value of a single component of the graphical object; and
Cs and Cdxe2x88x921 are from the same component as Cd.
A final image is generated, or rendered, utilizing a destination value for each component of each pixel of the combined objects. More specifically, for each pixel of the final image, a destination value is determined for a plurality of components. Particularly, the final image is generated from a red component, a green component, a blue component and an alpha component of each object. The final image is then rendered, or displayed, on a display for use by the physician or operator.
In use, the operator generates a graphical object to define a portion of the image object, for example, a region of interest. The system then combines the objects. As a result of the manner in which the objects are combined, the graphical image does not obscure the image object information. In one embodiment, the system alters the display characteristics of the graphical objects, by outlining or filling the graphical objects, so that the area covered by the graphical area is easily detected by the operator.
The above described overlay algorithm allows a physician or operator to select and display a defined graphical object, along with an image object generated by the imaging system, without the graphical object blocking or obscuring the object image. More specifically, each graphical object and image object are simultaneously displayed so that each object is fully visible. In addition, the described system defines the area covered by the graphical images by filling or outlining the graphical objects.